Lightguide and method for manufacturing the same

ABSTRACT

A lightguide having either a built-in prism sheet or a built-in diffuser sheet is disclosed. The lightguide includes: a prism sheet having a plane surface and a surface with a plurality of patterned microlens, a transparent wedge having a cross-section of trapezoid; and a binder layer sandwiched between said plane surface of said prism sheet and said transparent wedge. A method for manufacturing the lightguide is also disclosed here.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lightguide and, moreparticularly, to a lightguide for flat panel display devices and methodfor manufacturing the lightguides.

[0003] 2. Description of Related Art

[0004] Currently, lightguides are widely used in flat panel displaydevice (e.g. liquid crystal display device) to distribute the light ofbacklight module. Generally, a backlight module includes a lightguide, aplurality of prism sheets and a plurality of diffuser sheets. However,since many sheets are required in the traditional backlight module, thethickness of traditional backlight module is great and hard to bereduced.

[0005] In recent years, in order to reduce the thickness of thetraditional backlight module, a prismless backlight module is introducedto the flat panel display. However, the manufacturing processing of thecomponets of the prismless backlight module is complicated. The surfaceof the lightguide is required to form a plurality of microlens. It takeslong time to processing. Although this kind of lightguide can be madethrough inject molding, the cost for manufacturing molds is high. Thetime needs for manufacturing these kinds of molds is very long. Inaddition, the wearing of these kinds of molds is serious as they areused for mass-production, In other words, the lifetime of these moldsfor these lightguides is short. Therefore, these kinds of molds andlightguides are not suitable for being applied for mass-production.

[0006] Therefore, it is desirable to provide an improved speechrecognition method to mitigate the aforementioned problems.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to provide a lightguidewith low cost of material, low thickness and less weight.

[0008] Another object is to provide a lightguide having an additionalfunction for diffusing or distributing light.

[0009] Another object is to provide a method for manufacturing alighgtguide having an additional function for diffusing or distributinglight.

[0010] Another object is to provide a method for manufacturing variouslighgtguides with different patterns of prisms without cutting patternsof microlens on molds.

[0011] Another object is to provide a method for manufacturing variouslighgtguides through simple inject molding.

[0012] To achieve the object, the lightguide of the present inventionincludes: a prism sheet having a plane surface and a surface with aplurality of patterned microlens; a transparent wedge having across-section of trapezoid; and a binder layer sandwiched between saidplane surface of said prism sheet and said transparent wedge, whereinsaid binder and said prism sheet are made from substantially identicalor different materials

[0013] The laminated film of the present invention for manufacturing alightguide, comprising: a carrier sheet; a prism sheet having a planesurface and a patterned surface with a plurality of microlens; aprotection sheet sandwiched between said carrier sheet and saidpatterned surface of said prism sheet, wherein said protection sheet hasa patterned surface to contact with said prism sheet, and the pattern ofsaid patterned surface of said protection layer is complementary to thepattern of said prism, and a binder layer attached on said plane surfaceof said prism sheet; wherein said binder and said prism sheet are madefrom substantially identical or different materials.

[0014] Another laminated film of the present invention for manufacturinga lightguide, comprising: a carrier sheet; a prism sheet having a planesurface and a patterned surface with a plurality of microlens; adiffuser sheet sandwiched between said carrier sheet and said patternedsurface of said prism sheet, wherein said diffuser sheet has a patternedsurface to contact with said prism sheet, and the pattern of saidpatterned surface of said diffuser layer is complementary to the patternof said prism; a protection sheet for protecting said prism sheet orsaid diffuser sheet, wherein said protection sheet is sandwiched betweensaid carrier sheet and said diffuser sheet; a binder layer attached onsaid plane surface of said prism sheet; wherein said binder and saidprism sheet are made from substantially identical or differentmaterials.

[0015] The method of the present invention for manufacturing alightguide, comprising following steps: (A) providing a mold having alaminated film inside, said laminated film comprising: a carrier sheet;a prism sheet having a plane surface and a patterned surface with aplurality of microlens; a protection sheet sandwiched between saidcarrier sheet and said patterned surface of said prism sheet, whereinsaid protection sheet has a patterned surface to contact with said prismsheet, and the pattern of said patterned surface of said protectionlayer is complementary to the pattern of said prism; and a binder layerattached on said plane surface of said prism sheet; (B) injecting apolymer into said mold with said laminated film; (C) opening said moldand taking out the molding; and (D) releasing said carrier sheet andsaid protection sheet from said molding.

[0016] Another method of the present invention for manufacturing alightguide, comprising following steps: (A) providing a mold having alaminated film inside, said laminated film comprising: a carrier sheet;a prism sheet having a plane surface and a patterned surface with aplurality of microlens; a diffuser sheet sandwiched between said carriersheet and said patterned surface of said prism sheet, wherein saiddiffuser sheet has a patterned surface to contact with said prism sheet,and the pattern of said patterned surface of said diffuser layer iscomplementary to the pattern of said prism; a protection sheet forprotecting said prism sheet or said diffuser sheet, wherein saidprotection sheet is sandwiched between said carrier sheet and saiddiffuser sheet; a binder layer attached on said plane surface of saidprism sheet; wherein said binder and said prism sheet are made fromsubstantially identical or different materials; (B) injecting a polymerinto said mold with said laminated film; (C) opening said mold andtaking out the molding; and (D) releasing said carrier sheet and saidprotection sheet from said molding.

[0017] Other objects, advantages, and novel features of the inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view of the first embodiment of thelaminated film of the present invention.

[0019]FIG. 2 is a perspective view of the second embodiment of thelaminated film of the present invention.

[0020]FIG. 3 is a perspective view of method for manufacturing thelightguide of the present invention.

[0021]FIG. 4 is a perspective view of the second embodiment of thelightguide of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The binder used here can be any conventional binder. Generally,the binder of the present invention is an organic polymer with lowsoftening temperature or polymer compositions. The binder binds prismsheet and injected polymer as polymer is injected into the mold. Thematerials of binder can be identical as or different from that of thetransparent wedge for lightguide. The carrier can be a continuous ordiscontinuous material. The surface of the carrier can be either smoothor rough. The carrier cane be used alone. Or the carrier can be usedincorporated with release. Preferably, carrier is made from PET,ceramics, metals or rubber. The protection sheet can be made from anymaterials resistant to scratches, cuttings and impact. The lightguide ofthe present invention can selectively further comprises a patterneddiffuser sheet. The pattern of said diff-user sheet is selectivelycomplementary to the pattern of said prism sheet. The surface contraryto said patterned surface of said diffuser sheet can be either a planesurface or optionally a surface with substantially identical patterns.The transparent wedge can be made from any transparent materials.Preferably, the transparent wedge is made from polycarbonate orpolymethacrylate. The lightguide of the present invention can be usedfor any flat panel display devices. Preferably, the lightguide of thepresent invention can be used for a liquid crystal display device. Theprotection sheet of the present invention and the carrier sheet can beeither two different sheets. Optionally, the protection sheet of thepresent invention can be integrated with the carrier sheet. Thelaminated film can selectively further comprise a release layer. Therelease layer is sandwiched by said protection sheet and said prismsheet. In the method of the present invention for manufacturing alightguide, the laminated film can be supplied through any conventionalmethod. Preferably, the laminated film is provided or suppliedcontinuously

[0023] With reference to FIG, 1, there is shown the first embodiment ofthe laminated film of the present invention. The laminated film of thefirst embodiment of the invention is used for manufacturing a lightguidefor a flat panel display device (e.g. a liquid crystal display device).The laminated film 100 includes a carrier sheet 110, a protection sheet120, a release layer 130, a prism sheet 140 and a binder layer 150. Thecarrier sheet 110 acts as a matrix or a substrate for subsequentattachment of other sheets or layers. In the first embodiment of thepresent invention, the carrier sheet is a PET sheet. Beneath the carriersheet 110, there is a protection sheet 120. The protection sheet 120prevents prism sheet 140 from scratching, wearing or direct impact.Therefore, the pattern of microlens on the prism sheet 140 can be wellprotected and reserved. One of the surfaces of the prism sheet 140 ofthe first embodiment is filled with patterns of microlens. The patternof the microlens on the prism sheet 140 focuses most light (e.g. fromthe bottom of the laminated film 100) in the same direction (e.g. to thetop side of the laminated film 100) to increase the intensity of lighton the top surface of the laminated film 100. On the other hand, thesurface of the protection sheet is also a patterned surface. The patternon the surface of the protection sheet is just complementary to thepattern of the microlens of the prism sheet 140. In addition, the othersurface of the prism sheet 140 is a plane surface. The plane surface isselectively coated with a layer of binder 150. The binder layer 150 isused for subsequent combination with a transparent wedge. In the firstembodiment of the laminated film of the present invention, a releaselayer 130 is coated between the prism sheet 140 and the protection sheet120. The release layer 130 is designed to ease the molding with prismsheet 140 to release from the molds and the protection sheet 120 aftersubsequent transparent wedge is attached (e.g. through inject molding orextrusion molding). The carrier sheet 110 and the protection sheet 120can be selectively integrated as one layer to save the thickness orreduce the cost of materials.

[0024] The method for manufacturing a light guide can be shown in FIG.3. A laminated film 300 as illustrated above is attached and fixed onthe inside surface of a mold 310 for a lightguide. A polymer for formingthe transparent wedge of the lightguide is injected into the moldthrough an opening 312 after the mold is closed. The polymer used hereis PMMA (or polycarbaonate). As the polymer is injected into the mold310, the binder on the plane surface of the prism sheet is melt andcombined with the injected polymer. Therefore, as the transparent wedgeof the lightguide forms, the laminated film 300 and the transparentwedge will bind together. Then, the mold is opened and the molding istaken out from the mold. After the carrier sheet and the protectionsheet is released, a lightguide with prism sheet can be obtained.

[0025] With reference to FIG. 2, there is shown the second embodiment ofthe laminated film of the present invention. The laminated film of thesecond embodiment of the invention is also used for manufacturing alightguide for a flat panel display device (e.g. a liquid crystaldisplay device). The laminated film 200 includes a carrier sheet 210, aprotection sheet 220, a release layer 230, a prism sheet 240, a binderlayer 250 and a diffuser sheet 260. The carrier sheet 210 acts as amatrix or a substrate for subsequent attachment of other sheets orlayers. In the second embodiment of the present invention, the carriersheet is a PET sheet. Beneath the carrier sheet 210, there is aprotection sheet 220. Furthermore, beneath the protection sheet 220,there is a diffuser sheet 260. The protection sheet 220 prevents thediffuser sheet 260 from scratching, wearing or direct impact. Furtherbeneath the diffuser sheet 260, there is a prism sheet 240 withpatterned microlens. The other surface (bottom surface) of the prismsheet 240 is coated with a layer of binder 250. The bottom surface ofthe diffuser sheet 260 is a patterned surface. The pattern on thesurface of the diffuser sheet 260 is just complementary to the patternof the microlens of the prism sheet 240. he pattern of the microlens onthe prism sheet 240 focuses most light (e.g. from the bottom of thelaminated film 200) in the same direction (e.g. to the top side of thelaminated film 200) to increase the intensity of light on the topsurface of the laminated film 200. The diffuser sheet 260 helps todistribute the light from prism sheet 240 much more homogeneously. Thebinder layer 250 is used for subsequent combination with a transparentwedge. In the second embodiment of the laminated film 200 of the presentinvention, a release layer 230 is coated between the diffuser sheet 240and the protection sheet 220. The release layer 230 is designed to easethe molding with diffuser sheet 260 to release from the molds and theprotection sheet 220 after subsequent transparent wedge is attached(e.g. through inject molding or extrusion molding). Moreover, thecarrier sheet 210 and the protection sheet 220 can be selectivelyintegrated as one layer to save the thickness or reduce the cost ofmaterials.

[0026] A laminated film as illustrated in second embodiment is also usedfor the manufacturing of a lightguide. The steps for manufacturing alightguide with a laminated film as illustrated in second embodiment issimilar to that of laminated film as illustrated in first embodiment.The laminated film as illustrated in second embodiment is attached andfixed on the inside surface of a mold for a lightguide. A polymer forforming the transparent wedge of the lightguide is injected into themold through an opening after the mold is closed. The polymer used hereis polycarbaonate. As the polymer is injected into the mold , the binderon the plane surface of the prism sheet is melt and combined with theinjected polymer. Therefore, as the transparent wedge of the lightguideforms, the laminated film and the transparent wedge will bind together.Then, the mold is opened and the molding is taken out from the mold.After the carrier sheet and the protection sheet is released, alightguide with a built-in prism sheet 440, a built-in diffuser 450 andtransparent wedge 470 can be obtained (as shown in FIG. 4).

[0027] Since there is a built-in diffuser or a built-in prism inlightguide of the present invention, the lightguide of the presentinvention has function of a diffuser, a prism and a lightguide. In otherwords, one lightguide of the present invention functions as acombination of a conventional diffuser sheet, a conventional prism sheetand a lightguide. Therefore, compared with the traditional backlightmodule of a conventional lightguide and diffuse sheets, prism sheets,the thickness, the weight, and the cost of a backlight module with thelightguide of the present invention can be greatly reduced. On the otherhand, since a laminated film with predetermined pattern of prism sheetis used in the method for manufacturing a lightguide here, the patternof the prism can be changed very easily and quickly to meet any specialrequirement. The manufacturing method of the present invention saveslots of time and cost for cutting grooves on molds as the pattern of theprism is asked to change. Furthermore, it also saves space for storingmolds for manufacturing lightguides with different prism patterns. Inaddition, since the prism can be changed very quickly and frequently.The manufacturing method of the present invention can be applied tomass-production of lightguides very easily. Even the wearing of prismsheet is serious, new prism can be replaced very easily and quickly intoa mold (just change the laminated films). Therefore, the manufacturingmethod of the present invention is very easy for maintenance.

[0028] Although the present invention has been explained in relation toits preferred embodiment, it is to be understood that many otherpossible modifications and variations can be made without departing fromthe spirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. A lightguide comprising: a prism sheet having aplane surface and a surface with a plurality of patterned microlens; atransparent wedge having a cross-section of trapezoid; and a binderlayer sandwiched between said plane surface of said prism sheet and saidtransparent wedge, wherein said binder and said prism sheet are madefrom substantially identical or different materials.
 2. The lightguideas claimed in claim 1, further comprising a patterned diffuser sheet,wherein the pattern of said diffuser sheet is complementary to thepattern of said prism sheet.
 3. The lightguide as claimed in claim 2,wherein the other surface contrary to said patterned surface of saiddiffuser sheet is a plane surface.
 4. The lightguide as claimed in claim2, wherein the two contrary surfaces of said diffuser sheet havesubstantially identical patterns.
 5. The lightguide as claimed in claim1, wherein said transparent wedge is made from polycarbonate orpolymethacrylate.
 6. The lightguide as claimed in claim 1, wherein saidlightguide applied for a liquid crystal display device.
 7. A laminatedfilm for manufacturing a lightguide, comprising: a carrier sheet; aprism sheet having a plane surface and a patterned surface with aplurality of microlens; a protection sheet sandwiched between saidcarrier sheet and said patterned surface of said prism sheet, whereinsaid protection sheet has a patterned surface to contact with said prismsheet, and the pattern of said patterned surface of said protectionlayer is complementary to the pattern of said prism; and a binder layerattached on said plane surface of said prism sheet; wherein said binderand said prism sheet are made from substantially identical or differentmaterials.
 8. The laminated film as claimed in claim 7, wherein saidprotection sheet is integrated with said carrier sheet.
 9. The laminatedfilm as claimed in claim 7, further comprising a release layer, whereinsaid release layer is sandwiched by said protection sheet and said prismsheet.
 10. A laminated film for manufacturing a lightguide, comprising:a carrier sheet; a prism sheet having a plane surface and a patternedsurface with a plurality of microlens; a diffuser sheet sandwichedbetween said carrier sheet and said patterned surface of said prismsheet, wherein said diffuser sheet has a patterned surface to contactwith said prism sheet, and the pattern of said patterned surface of saiddiffuser layer is complementary to the pattern of said prism; aprotection sheet for protecting said prism sheet or said diffuser sheet,wherein said protection sheet is sandwiched between said carrier sheetand said diffuser sheet; and a binder layer attached on said planesurface of said prism sheet; wherein said binder and said prism sheetare made from substantially identical or different materials.
 11. Thelaminated film as claimed in claim 10, wherein said protection sheet isintegrated with said carrier sheet.
 12. The laminated film as claimed inclaim 10, further comprising a release layer, wherein said release layeris sandwiched by said protection sheet and said prism sheet.
 13. Amethod for manufacturing a lightguide, comprising following steps: (A)providing a mold having a laminated film inside, said laminated filmcomprising: a carrier sheet; a prism sheet having a plane surface and apatterned surface with a plurality of microlens; a protection sheetsandwiched between said carrier sheet and said patterned surface of saidprism sheet, wherein said protection sheet has a patterned surface tocontact with said prism sheet, and the pattern of said patterned surfaceof said protection layer is complementary to the pattern of said prism;and a binder layer attached on said plane surface of said prism sheet;(B) injecting a polymer into said mold with said laminated film; (C)opening said mold and taking out the molding; and (D) releasing saidcarrier sheet and said protection sheet from said molding.
 14. Themethod as claimed in claim 13, wherein said protection sheet isintegrated with said carrier sheet.
 15. The method as claimed in claim13, wherein said laminated film is provided or supplied continuously.16. The method as claimed in claim 13, wherein said laminated filmfurther comprising a release layer sandwiched by said protection sheetand said prism sheet.
 17. A method for manufacturing a lightguide,comprising following steps: (A) providing a mold having a laminated filminside, said laminated film comprising: a carrier sheet; a prism sheethaving a plane surface and a patterned surface with a plurality ofmicrolens; a diffuser sheet sandwiched between said carrier sheet andsaid patterned surface of said prism sheet, wherein said diffuser sheethas a patterned surface to contact with said prism sheet, and thepattern of said patterned surface of said diffuser layer iscomplementary to the pattern of said prism; a protection sheet forprotecting said prism sheet or said diffuser sheet, wherein saidprotection sheet is sandwiched between said carrier sheet and saiddiffuser sheet; and a binder layer attached on said plane surface ofsaid prism sheet; wherein said binder and said prism sheet are made fromsubstantially identical or different materials; (B) injecting a polymerinto said mold with said laminated film; (C) opening said mold andtaking out the molding; and (D) releasing said carrier sheet and saidprotection sheet from said molding.
 18. The method as claimed in claim17, wherein said protection sheet is integrated with said carrier sheet.19. The method as claimed in claim 17, wherein said laminated film isprovided or supplied continuously.
 20. The method as claimed in claim17, wherein said laminated film further comprising a release layersandwiched by said protection sheet and said prism sheet.